1. Field of the Invention
The present invention relates to a plasma treatment system which generates plasma in a perfusion layer of an electrically conductive solution by the passage of a radio-frequency current through the perfusion layer across a first electrode portion and a second electrode portion that are provided in a treatment portion, and uses the generated plasma to treat a treated target.
2. Description of the Related Art
Jpn. Pat. Appln. KOKAI Publication No. 2011-45756 has disclosed a plasma treatment system including a treatment instrument in which a first electrode portion (active electrode) and a second electrode portion (return electrode) are provided in a treatment portion of a probe. In this plasma treatment system, the first electrode portion is provided in a state where the position thereof relative to the second electrode portion does not change. The treatment instrument is provided with a sheath through which a probe is inserted in a state where the treatment portion protrudes toward the distal direction. A supply path is formed between the sheath and the probe, and a spout of the supply path is formed at the distal end of the sheath. A suction path is formed inside the probe, and a suction hole of the suction path is formed on the distal surface of the treatment portion. In a treatment, an electrically conductive solution (physiological saline) is supplied through the supply path, and the supplied electrically conductive solution is sucked through the suction path. Consequently, in the treatment, a perfusion layer of the electrically conductive solution from the spout of the supply path toward the suction hole of the suction path is formed between a treated target and the treatment portion.
By the transmission of radio-frequency energy (radio-frequency electric power) to the first electrode portion and the second electrode portion in a state where the first electrode portion and the second electrode portion are immersed in the perfusion layer, a radio-frequency current flows between the first electrode portion and the second electrode portion in the perfusion layer. If a voltage between the first electrode portion and the second electrode portion is increased, the radio-frequency current flows through the perfusion layer of the electrically conductive solution, and a vapor layer is thereby formed between the first electrode portion and the second electrode portion of the perfusion layer. Further, a breakdown occurs in the vapor layer, and plasma is generated in the perfusion layer of the electrically conductive solution. In the treatment, a treated target such as a living tissue is ablated by the generated plasma. Such a treatment is referred to as a low-temperature ablation treatment, and is used in, for example, the resection of a tonsil. The control of the radio-frequency energy transmitted to the first electrode portion and the second electrode portion and others are performed by a plasma treatment control unit.